The present invention relates to a device for varying the resistance of electrical circuits (a potentiometer) in combination with a device for changing the state of a current conductor (electrical switch).
Such devices are widely employed as components in various forms and sizes in electronic assemblies, industrial control and regulation installations, and the like.
The combination of a potentiometer with a switch for changing the electrical conduction in the same or in another circuit, is a useful feature in the operation of many types of electronic assemblies and installations in industrial, professional, and retail application.
The improvements herein described contribute to the rationalization of production of the devices in question insofar as, given the specific function carried out by each of them, they can be manufactured as separate components, namely a device for the progressive variation of electrical resistance, and a device for instant change in electrical conduction, respectively. The two devices can then be functionally combined, both having been provided with means by which their respective moving parts can fulfill their function in mutual coordination, a rotary motion through common control means.
Thus, when the cursor of the potentiometer has traced out its full angle of movement and reached one extremity of its resistance track, a continuity change will occur, for example the switch will open. On reversing the rotational movement applied to the control means of the variable resistance device another continuity change will occur, in the reverse sense to the previous one, that is to say, the switch will close, while also producing a variation, in the reverse sense to the previous variation, of the electrical resistance which exists between each of the terminals of the resistance track and the cursor.
Another characteristic of the combined device of this invention is the possibility of each of the two components being assembled automatically. The assembly process of the respective components is independent, and the two can then be combined subsequent to the completion of their respective assemblies.
In a preferred version of the assembly procedure of the variable resistance, the metal parts thereof, consisting principally in the terminals contacting the extremities of the resistance track and the collector leading to another terminal, are obtained by stamping from a sheet metal strip having the appropriate characteristics, in a continuous feed system on an assembly line. The preferred version would utilize, for example, an electrolitic brass strip which would undergo a primary stamping operation producing the approximate form of the terminals and the collector, passing them to a metallization process applying a different metal to the two respective faces, such as tin and nickel or copper. The stamped out metallized strip can then proceed, without need of any supplementary support, to the assembly machine, wherein it will receive its final cut to shape, with the parts being formed into their characteristic structure, ready for immediate assembly, with the other parts making up the respective device.
In this manner are produced equally the continuity change devices for combination with the variable resistance devices and which can be attached to the former when it is required to make up one single functional unit with one common control, resulting thus in a pair of devices in combination in one body. The attachment of the body to a support, such as the frame of a machine, or an electronic assembly, presents no difficulty and the terminals which are accessible can be connected to the extremities of the conductors associated with diverse components comprising the remainder of the circuit in question.
The improvements to be described cover the production of the variable resistance device in such a manner that in the absence of the continuity change device the component carrying the rotating cursor terminates in a coaxial extension which can remain free, with no specific purpose. When it is required to effect a combination of the two devices the central extended prolongation of the cursor carrying component is coupled mechanically to the component of the continuity change device which has to actuate the moving part carrying a contact point which eventually comes into contact with a similar contact point on a fixed part of the device.